1. Field of the Invention
The invention relates to an illumination system.
2. Description of Related Art
There is known a display device including an array of on/off switchable elements, such as a spatial modulator (digital mirror) formed of movable micromirrors that deflect light irradiated from a light source. In a display device described in Japanese Patent No. 3844013, a gray scale is provided by using time division modulation in order to change each element between an on state where light is directed toward a display and an off state where light is not directed toward the display. That is, by carrying out on/off switching at a high speed (high-frequency drive) through control over a duty ratio, intermediate brightness between the on state and the off state is presented (see Japanese Patent No. 3844013).
A projection device described in Japanese Patent Application Publication No. 2013-76923 (JP 2013-76923 A) includes projection means including a projection optics system that forms and projects a light figure corresponding to an image signal by using light from a light source. In this projection device, “blur lighting” that blurs the periphery of a projected image is achieved by, for example, adjusting the focus to a non-focus state where the projection optics system sets a zoom angle of view to the maximum angle of view (adjusting the optics system) (see JP 2013-76923 A).
There is suggested a vehicle illumination system that controls light distribution with a digital mirror including a plurality of movable micromirrors (see Japanese Patent Application Publication No. 2012-190594 (JP 2012-190594 A)). There is also suggested a vehicle headlamp system that automatically shades part of an illumination area in order to prevent glare during traveling (see Japanese Patent Application Publication No. 2011-051441 (JP 2011-051441 A)).
However, in the vehicle illumination system that controls light distribution with the digital mirror, when part of the illumination area is shaded, the boundary between a shaded area within the illumination area and an irradiated area adjacent to the shaded area becomes distinct, so there is an inconvenience that a visual feeling of strangeness arises.
A method of blurring the boundary between a shaded area and an irradiated area includes, for example, the method described in Japanese Patent No. 3844013, which carries out high-frequency drive, and the method described in JP 2013-76923 A, which adjusts the optics system. However, the former has such an inconvenience that the service life of the digital mirror becomes short because of high-frequency drive, and the latter has such an inconvenience that a new movable optics system is required.